Charcot-Marie-Tooth (CMT) disease is a group of inherited disorders that specifically affect the peripheral nerves system and is characterized by progressive muscle atrophy, sensory loss and bone deformities. This genetic disease, for which there is no effective therapy, is one of the most commonly inherited neurological disorders affecting approximately 1 in 2,500 people equating to approximately 125,000 people in the United States. Multiple mutations in four different aminoacyl-tRNA synthetase genes are causally linked to CMT. Thus tRNA synthetases are one of the largest gene families associated with CMT. This underscores the importance of tRNA synthetase in the etiology of the disease. Understanding the connection between CMT and tRNA synthetases is a challenge. Because tRNA synthetases are essential players in protein synthesis, the dogma has been that the CMT-causing mutations in tRNA synthetases must affect protein synthesis in some way. Intriguingly, CMT-causing mutations do not necessarily affect the aminoacylation function of the enzyme; and almost all tRNA synthetase mutations that are CMT-associated have autosomal dominant trait, suggesting a gain-of-function disease mechanism. Lastly, as protein synthesis is essential for all tissue types, the extreme tissue specificity associated with the CMT phenotypes has complicated the biological understanding of the role of tRNA synthetases in CMT disease. The goal of this project is to determine the disease-causing mechanism for DI-CMTC, a subtype of CMT caused by dominant mutations in tyrosine tRNA synthetase (TyrRS or YARS). Through international collaborations and a cross-disciplinary approach that combines methods of Drosophila genetics, biochemistry and cell and molecular biology, we will define the mechanism through which YARS mutations are linked to DI-CMTC. Broadly speaking, the tRNA synthetase family represents one class of DNA/RNA binding proteins that, as a whole, have emerged as an important player in neurodegenerative processes and as potential targets for therapeutic development. Thus, the mechanistic understanding we will obtain from the current study would certainly shed light on the etiology of other neurological disorders beyond CMT.